Conventionally, the main application of a speaker mounted in a mobile terminal such as a mobile telephone is to produce a ringing tone and ringing melody to inform the user of the mobile telephone of an incoming call. Mobile terminals with a videophone function and mobile terminals with the hand-free communication function of producing an incoming sound from the speaker have become popular. A playback function of playing back video clips captured by the user has improved greatly. Also, the video clip delivery service has become popular. Along with these trends, the speaker characteristics must be ensured when the user listens to the sound and music while observing the display content of the mobile terminal.
As a method of improving the speaker characteristics when the user listens to the incoming sound, music, and the like while observing the display content, the position of a speaker sound emission hole (a hole portion through which a sound output from the speaker is emitted) arranged in the housing of the mobile terminal may be changed. For example, in a mobile telephone, a speaker sound emission hole is frequently arranged in the rear side (for example, a surface opposite to a surface where a display and operation unit are present) of the housing. The speaker sound emission hole may, however, be arranged not on the rear side of the housing but in the side surface of the housing. By arranging the speaker sound emission hole in the side surface of the housing, the directivity of the sound emitted from the speaker with respect to the front side of the display can be improved, so that the speaker characteristics can be improved.
Delivery of contents (e.g., a video image) subjected to a DSP process to have a virtual 3D (three-dimensional) effect and delivery of music subjected to a DSP process to have a virtual surround effect have been introduced. Accordingly, stereo-sound mobile telephones each mounted with two speakers are increasing. In this case, in order to obtain the stereo effect, the sounds generated by the respective speakers must be emitted from separate positions in two directions. Hence, mobile telephones in each of which speaker sound holes are arranged in the left and right side surfaces of the housing are increasing.
In a folding mobile telephone which is currently becoming most popular, speakers are frequently packaged on the rear side of a display side housing in which a speech receiver is packaged. As the apparatus (mobile terminal) becomes thinner, a reduction (particularly thickness reduction) of the packaging space for the speaker is required. To make the speaker packaging space thin, thickness reduction of the speaker and that of a packaging structure to arrange the speaker sound hole in the housing side surface of the mobile terminal are required.
As a packaging structure for a speaker in a stereo-sound mobile telephone, for example, Japanese Patent Laid-Open No. 2003-152837 (reference 1) describes a mobile telephone mounted with twin speakers. FIG. 15 is a sectional view showing the speaker packaging structure of the mobile telephone mounted with the twin speakers described in reference 1. As shown in FIG. 15, in the mobile telephone described in reference 1, output sounds of left and right speakers are emitted from two sound emission holes 81a and 81b formed in the left and right side surfaces of a rear side housing 81.
More specifically, in the mobile telephone described in reference 1, two compact speakers 82a and 82b are axis-symmetrically packaged in the rear housing to be horizontal with respect to the rear housing. The speakers 82a and 82b are arranged such that the speaker front surfaces where the sounds are output oppose the rear side housing 81. Cavities 83a and 83b formed between the rear side housing 81 and the respective speakers 82a and 82b are utilized as acoustic transfer spaces from the speakers 82a and 82b to the sound emission holes 81a and 81b of the housing. The respective speaker sounds are emitted from the two sound emission holes 81a and 81b formed in the housing.